For #19016
This changes all the places where we previously assumed that certs were
hardcoded when the Fleet server started to query the database instead.
The plan is to loadtest afterwards, but as a first preemptive measure,
this adds a caching layer on top the mysql datastore.
# Checklist for submitter
If some of the following don't apply, delete the relevant line.
<!-- Note that API documentation changes are now addressed by the
product design team. -->
- [x] Added/updated tests
- [x] If database migrations are included, checked table schema to
confirm autoupdate
- For database migrations:
- [x] Checked schema for all modified table for columns that will
auto-update timestamps during migration.
- [x] Confirmed that updating the timestamps is acceptable, and will not
cause unwanted side effects.
- [x] Ensured the correct collation is explicitly set for character
columns (`COLLATE utf8mb4_unicode_ci`).
- [x] Manual QA for all new/changed functionality
for #13703 and #13992, this updates the logic used by the functions that
gather hosts that need DEP profile updates to use hosts directly from
`host_dep_assignments`, regardless of their MDM status.
